1. Field of the Invention
The invention concerns a process for the controlled discharge of activity from a reactor containment building of a gas cooled nuclear power plant. The invention also relates to the power plant having a reactor containment building which, as a barrier against the release of active cooling gas to the environment, encloses the nuclear power plant and is equipped with a discharge circuit for cooling gas leakages occurring during normal operation. The discharge circuit includes an operational filter system, exhaust gas blower and a stack.
2. Background of the Art
The state-of-the-art includes nuclear power plants comprising high temperature reactors installed within reactor pressure vessels. These vessels are in turn surrounded by a containment vessel or containment building. One of the functions of a containment building is to prevent the release of fission products to the environment. In the case of the known AVR (from the German word Atomversuchsreaktor which translates as Experimental Atomic Reactor) nuclear power plant, the containment vessel is under a slightly negative pressure during operation in order to prevent leakage from the primary circuit into the atmosphere. Because the AVR installation uses fuel elements coated with fission material particles, the activity of the cooling gas in the primary circuit is slight to begin with. In the nuclear power plants with high temperature reactors, it is specified to the containment vessel for pressures that enable the containment vessel to absorb any leakage occurring in operation and due to incidents of reactor failure or nuclear accident. This design is known as full pressure containment. It is also known in these power plants to discharge the cooling gas leakages originating in the reactor pressure vessel and the radioactive circuits to the environment in a delayed manner through filter paths and a stack. Even in the case of severe incidents, such as the failure of a seal of the reactor pressure vessel, the exiting cooling gas is retained and discharged through the filter and the stack in a controlled manner. The effects of the incident remain limited in this manner.
In the THTR=300 nuclear power plant, the discharge of cooling gas leakages occurring during normal operation and in minor incidents is effected into the atmosphere through a filter system, an exhaust air blower and a stack. The reactor containment building surrounding the reactor pressure vessel is not laid out, however, for containment of the full pressure. In the case of incidents releasing large amounts of a leakage, these leakages are released to the atmosphere unfiltered through the stack to the environment.